Disrupted Calcium Signaling in Animal Models of Human Spinocerebellar Ataxia (SCA)

Spinocerebellar ataxias (SCAs) constitute a heterogeneous group of more than 40 autosomal-dominant genetic and neurodegenerative diseases characterized by loss of balance and motor coordination due to dysfunction of the cerebellum and its efferent connections. Despite a well-described clinical and pathological phenotype, the molecular and cellular events that underlie neurodegeneration are still poorly undaerstood. Emerging research suggests that mutations in SCA genes cause disruptions in multiple cellular pathways but the characteristic SCA pathogenesis does not begin until calcium signaling pathways are disrupted in cerebellar Purkinje cells. Ca2+ signaling in Purkinje cells is important for normal cellular function as these neurons express a variety of Ca2+ channels, Ca2+-dependent kinases and phosphatases, and Ca2+-binding proteins to tightly maintain Ca2+ homeostasis and regulate physiological Ca2+-dependent processes. Abnormal Ca2+ levels can activate toxic cascades leading to characteristic death of Purkinje cells, cerebellar atrophy, and ataxia that occur in many SCAs. The output of the cerebellar cortex is conveyed to the deep cerebellar nuclei (DCN) by Purkinje cells via inhibitory signals; thus, Purkinje cell dysfunction or degeneration would partially or completely impair the cerebellar output in SCAs. In the absence of the inhibitory signal emanating from Purkinje cells, DCN will become more excitable, thereby affecting the motor areas receiving DCN input and resulting in uncoordinated movements. An outstanding advantage in studying the pathogenesis of SCAs is represented by the availability of a large number of animal models which mimic the phenotype observed in humans. By mainly focusing on mouse models displaying mutations or deletions in genes which encode for Ca2+ signaling-related proteins, in this review we will discuss the several pathogenic mechanisms related to deranged Ca2+ homeostasis that leads to significant Purkinje cell degeneration and dysfunction.

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Activation of MAP3K DLK and LZK in Purkinje Cells Causes Rapid and Slow Degeneration Depending on Signaling Strength

10.1101/2020.10.09.332940 ◽

2020 ◽

Author(s):

Yunbo Li ◽

Erin M Ritchie ◽

Christopher L. Steinke ◽

Cai Qi ◽

Lizhen Chen ◽

...

Keyword(s):

Alternative Splicing ◽

Purkinje Cell ◽

Purkinje Cells ◽

Leucine Zipper ◽

Activity Levels ◽

Cell Type ◽

Cell Degeneration ◽

Mechanistic Basis ◽

Cerebellar Purkinje Cells ◽

Jnk Activation

SummaryThe conserved MAP3K Dual leucine zipper kinases can activate JNK via MKK4 or MKK7. Vertebrate DLK and LZK share similar biochemical activities and undergo auto-activation upon increased expression. Depending on cell-type and nature of insults DLK and LZK can induce pro-regenerative, pro-apoptotic or pro-degenerative responses, although the mechanistic basis of their action is not well understood. Here, we investigated these two MAP3Ks in cerebellar Purkinje cells using loss- and gain-of function mouse models. While loss of each or both kinases does not cause discernible defects in Purkinje cells, activating DLK causes rapid death and activating LZK leads to slow degeneration. Each kinase induces JNK activation and caspase-mediated apoptosis independent of each other. Significantly, deleting CELF2, which regulates alternative splicing of Mkk7, strongly attenuates Purkinje cell degeneration induced by activation of LZK, but not DLK. Thus, controlling the activity levels of DLK and LZK is critical for neuronal survival and health.

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Expression of the yes proto-oncogene in cerebellar Purkinje cells.

Molecular and Cellular Biology ◽

10.1128/mcb.9.10.4545 ◽

1989 ◽

Vol 9 (10) ◽

pp. 4545-4549 ◽

Cited By ~ 18

Author(s):

M Sudol ◽

C F Kuo ◽

L Shigemitsu ◽

A Alvarez-Buylla

Keyword(s):

In Situ Hybridization ◽

Purkinje Cell ◽

Gene Product ◽

Purkinje Cells ◽

Immunofluorescent Staining ◽

Cell Degeneration ◽

Functional Studies ◽

Cerebellar Purkinje Cells ◽

The Brain

To identify the kinds of cells in the brain that express the yes proto-oncogene, we examined chicken brains by using immunofluorescent staining and in situ hybridization. Both approaches showed that the highest level of the yes gene product was in cerebellar Purkinje cells. In addition, we analyzed Purkinje cell degeneration (pcd) mutant mice. The level of yes mRNA in cerebella of pcd mutants was four times lower than that found in cerebella of normal littermates. Our studies point to Purkinje cells as an attractive model for functional studies of the yes protein.

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Activation of MAP3K DLK and LZK in Purkinje cells causes rapid and slow degeneration depending on signaling strength

eLife ◽

10.7554/elife.63509 ◽

2021 ◽

Vol 10 ◽

Author(s):

Yunbo Li ◽

Erin M Ritchie ◽

Christopher L Steinke ◽

Cai Qi ◽

Lizhen Chen ◽

...

Keyword(s):

Alternative Splicing ◽

Purkinje Cell ◽

Purkinje Cells ◽

Leucine Zipper ◽

Activity Levels ◽

Cell Type ◽

Cell Degeneration ◽

Mechanistic Basis ◽

Cerebellar Purkinje Cells ◽

Jnk Activation

The conserved MAP3K Dual-Leucine-Zipper Kinase (DLK) and Leucine-Zipper-bearing Kinase (LZK) can activate JNK via MKK4 or MKK7. These two MAP3Ks share similar biochemical activities and undergo auto-activation upon increased expression. Depending on cell-type and nature of insults DLK and LZK can induce pro-regenerative, pro-apoptotic or pro-degenerative responses, although the mechanistic basis of their action is not well understood. Here, we investigated these two MAP3Ks in cerebellar Purkinje cells using loss- and gain-of function mouse models. While loss of each or both kinases does not cause discernible defects in Purkinje cells, activating DLK causes rapid death and activating LZK leads to slow degeneration. Each kinase induces JNK activation and caspase-mediated apoptosis independent of each other. Significantly, deleting CELF2, which regulates alternative splicing of Map2k7, strongly attenuates Purkinje cell degeneration induced by LZK, but not DLK. Thus, controlling the activity levels of DLK and LZK is critical for neuronal survival and health.

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Calcium imaging reveals coordinated simple spike pauses in populations of Cerebellar Purkinje cells

10.1101/051730 ◽

2016 ◽

Author(s):

Jorge E. Ramirez ◽

Brandon M. Stell

Keyword(s):

Purkinje Cell ◽

Purkinje Cells ◽

Calcium Imaging ◽

Spatial Organization ◽

Cell Activity ◽

Cerebellar Nuclei ◽

Deep Cerebellar Nuclei ◽

Firing Rates ◽

Simple Spike ◽

Cerebellar Purkinje Cells

The brain’s control of movement is thought to involve coordinated activity between cerebellar Purkinje cells. The results reported here demonstrate that somatic Ca2+ imaging is a faithful reporter of Na+-dependent “simple spike” pauses and enables us to optically record changes in firing rates in populations of Purkinje cells. This simultaneous calcium imaging of populations of Purkinje cells reveals a striking spatial organization of pauses in Purkinje cell activity between neighboring cells. The source of this organization is shown to be the presynaptic GABAergic network and blocking GABAARs abolishes the synchrony. These data suggest that presynaptic interneurons synchronize (in)activity between neighboring Purkinje cells and thereby maximize their effect on downstream targets in the deep cerebellar nuclei.

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Purkinje cell degeneration associated with erythroid ankyrin deficiency in nb/nb mice.

The Journal of Cell Biology ◽

10.1083/jcb.114.6.1233 ◽

1991 ◽

Vol 114 (6) ◽

pp. 1233-1241 ◽

Cited By ~ 68

Author(s):

L L Peters ◽

C S Birkenmeier ◽

R T Bronson ◽

R A White ◽

S E Lux ◽

...

Keyword(s):

Purkinje Cell ◽

Purkinje Cells ◽

Granule Cells ◽

Cell Loss ◽

Chromosome 8 ◽

Cell Degeneration ◽

Purkinje Cell Loss ◽

Cell Stability ◽

Cerebellar Purkinje Cells

Mice homozygous for the nb mutation (Chromosome 8) have a severe hemolytic anemia and develop a psychomotor disorder at 6 mo of age. The nb/nb mice are deficient in erythroid ankyrin (Ank-1) but, until the present study, the role of Ank-1 and of Ank-2 (brain ankyrin) in disease genesis was unknown. In normal erythroid tissues, we show that two major transcripts are expressed from Ank-1, and one of these is also present at high levels in the cerebellum. By in situ hybridization and immunocytochemistry, Ank-1 localizes to the cerebellar Purkinje cells and, to a lesser extent, the granule cells. In nb/nb mice, Ank-1 transcripts are markedly reduced in both erythroid and neural tissue, and nb/nb Purkinje cells and granule cells are nearly devoid of Ank-1. The neurological syndrome appears concurrently with a dramatic loss of Purkinje cells. Ank-2 maps to Chromosome 3 and its expression is unaffected by the nb mutation. We conclude that Ank-1 is specifically required for Purkinje cell stability and, in its absence, Purkinje cell loss and neurological symptoms appear.

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Expression of the yes proto-oncogene in cerebellar Purkinje cells

Molecular and Cellular Biology ◽

10.1128/mcb.9.10.4545-4549.1989 ◽

1989 ◽

Vol 9 (10) ◽

pp. 4545-4549

Author(s):

M Sudol ◽

C F Kuo ◽

L Shigemitsu ◽

A Alvarez-Buylla

Keyword(s):

In Situ Hybridization ◽

Purkinje Cell ◽

Gene Product ◽

Purkinje Cells ◽

Immunofluorescent Staining ◽

Cell Degeneration ◽

Functional Studies ◽

Cerebellar Purkinje Cells ◽

The Brain

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Amelioration of the Behavioral Phenotype in Genetically Ataxic Mice through Bilateral Intracerebellar Grafting of Fetal Purkinje Cells

Cell Transplantation ◽

10.1177/096368979600500215 ◽

1996 ◽

Vol 5 (2) ◽

pp. 269-277 ◽

Cited By ~ 19

Author(s):

Lazaros C. Triarhou ◽

Zei Zhang ◽

Wei-Hua Le

Keyword(s):

Purkinje Cells ◽

Motor Performance ◽

Motor Coordination ◽

Dendritic Tree ◽

Cerebellar Nuclei ◽

Wild Type ◽

Cell Degeneration ◽

Gene Effects ◽

Neuron Populations ◽

Behavioral Paradigm

We have previously applied neural grafting to “Purkinje cell degeneration” mutant mice (gene symbol pcd, mouse chromosome 13), a model of recessively inherited cerebello-olivary atrophy, to create appropriate interactions between wild-type and mutant cells in elucidating gene effects on the involved neuron populations and to address issues of the structural integration of donor Purkinje cells into the disrupted cerebellar loop. Behaviorally, pcd homozygotes manifest ataxic signs beginning at 3-4 wk of age. The functional effects of cerebellar transplants on motor performance have long remained an open question. The aim of the present study was to determine the recovery of motor responses in pcd mutants in a battery of behavioral tasks after bilateral transplantation of cerebellar cell suspensions (prepared from wild-type mice) into the parenchyma of the deep cerebellar nuclei of the hosts, according to a protocol that emphasizes the reconstruction of the missing inhibitory cortico-nuclear projection. With this approach, the denervated deep nuclei of the host receive a new Purkinje axonal innervation; further, most transplanted Purkinje cells end up occupying cortical localities anyway and display a correct dendritic tree orientation toward the pia. Motor coordination and fatigue resistance were assessed in a rotarod treadmill apparatus, a behavioral paradigm useful in studying various brain abiotrophies and treatments, including developmental perturbations of the cerebellar cytoarchitecture. Locomotor activity was quantified by the number of squares mice crossed as they moved about in an open-field matrix. Grafted pcd mice performed significantly better than sham-operated mutants in both of these tasks. Moreover, graft-recipient mice were able to sustain their abdomen above the floor on their limbs during movement, contrasting to the typical lowered, widened stance of sham-operated pcd mutants. These findings clearly demonstrate that bilateral transplants of fetal Purkinje cells have functional effects on motor performance in the pcd model of hereditary cerebellar ataxia.

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Modulatory Effects of Monoamines and Perineuronal Nets on Output of Cerebellar Purkinje Cells

Frontiers in Neural Circuits ◽

10.3389/fncir.2021.661899 ◽

2021 ◽

Vol 15 ◽

Author(s):

Moritoshi Hirono ◽

Fuyuki Karube ◽

Yuchio Yanagawa

Keyword(s):

Purkinje Cells ◽

Motor Coordination ◽

Gaba Release ◽

Cerebellar Nuclei ◽

Brain Regions ◽

Perineuronal Nets ◽

Gabaergic Transmission ◽

Neural Connections ◽

Brain Functions ◽

Cerebellar Purkinje Cells

Classically, the cerebellum has been thought to play a significant role in motor coordination. However, a growing body of evidence for novel neural connections between the cerebellum and various brain regions indicates that the cerebellum also contributes to other brain functions implicated in reward, language, and social behavior. Cerebellar Purkinje cells (PCs) make inhibitory GABAergic synapses with their target neurons: other PCs and Lugaro/globular cells via PC axon collaterals, and neurons in the deep cerebellar nuclei (DCN) via PC primary axons. PC-Lugaro/globular cell connections form a cerebellar cortical microcircuit, which is driven by serotonin and noradrenaline. PCs’ primary outputs control not only firing but also synaptic plasticity of DCN neurons following the integration of excitatory and inhibitory inputs in the cerebellar cortex. Thus, strong PC-mediated inhibition is involved in cerebellar functions as a key regulator of cerebellar neural networks. In this review, we focus on physiological characteristics of GABAergic transmission from PCs. First, we introduce monoaminergic modulation of GABAergic transmission at synapses of PC-Lugaro/globular cell as well as PC-large glutamatergic DCN neuron, and a Lugaro/globular cell-incorporated microcircuit. Second, we review the physiological roles of perineuronal nets (PNNs), which are organized components of the extracellular matrix and enwrap the cell bodies and proximal processes, in GABA release from PCs to large glutamatergic DCN neurons and in cerebellar motor learning. Recent evidence suggests that alterations in PNN density in the DCN can regulate cerebellar functions.

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